Commutator



COMMUTATOR Filed March 25, 1938 2 Sheets-Sheet l f2.5? @e-127%?? Hiv/nCr/ @arche/"5 A. c. BQRCHERS 2236,25?

COMMUTATOR `Filed March 23, 1938 2 Sheets-Sheet' 2 INVENTOR Him Caf/orcfzers ATTORNEY.

Patented Mar. 25, 1941 UNITED STATES PATENT OFFICE 2,236,251 continuaronApplication March 23,

1i) Claims.

This invention relates to commutators for electro-motive apparatus, andmore particularly to an improved methodof forming and arranging thecommutator segments in an insulating body.

Heretofore, it has been common practice in constructing motors withwhich I am familiar, to mold graphite into the brushes to reduceoperating noise of the motor. However, the material forming the brushesis necessarily softer than that of the commutator and as the brushesbecome worn, the graphite dust falls into the insulating spacel betweenthe commutator bars resulting in smudging of the bars and also sludg.ing between bars.

l have provided a commutator shell formed of molded copper and graphite,the amount of graphite being dependent on the lubricating qualitiesdesired and the requirements as to a proper soldering joint. Theresulting product may be more easily machined than drawn copper, mostgenerally used in huilt up commutators, although providing a very hardsurface and permitting closer tolerances in machining than with drawncopper or the like. Y

l combine the molded shell with an insulating body formed of phenoliccondensate material or the like so that when the shell is subseduentlydivided to form individual commutator bars, the bars are rigidlyanchored. Additionally, l may provide improved ventilator means for thecommutator to reduce the heating eiect on the commutator and brushes andthereby increase the useful life of the brushes.

may also form the shell oi molded pure copper dust without the additionoi' graphite wherein various advantages oi manufacture may be achievedas to a drawn copper shell such as relative ease in machining andworking to closer tolerances together with the fact that the moldedconstruction permits of an improved design with a minimum of machineoperations and waste material.

Also, I have provided an improved design ior commutator shells wherebythe necessity of saw cuts or the like to separate the shell into barsmay be eliminated and this may be effected by a shell shaving operation.y

It is an object of my invention therefore, to provide an improvedcommutator for electromotive apparatus.

Another object of my invention is to provide an improved method offorming electrical conducting material.

Another object of my invention is to provide 1938, Serial No. 197,653(ci. 1v1-321) improved means for anchoring commutator bars in aninsulating body.

Another object of my invention is to provide a commutator havingimproved Ventilating means associated therewith.

Another object of my invention is to provide an improved commutatorhaving a lubricant material molded thereinto and which may be machinedwith relatively close tolerances.

Another object of my invention is, to provide an improved commutatorwhich is relatively inexpensive to manufacture and has improvedoperating characterlstics` Another object of my invention is t eliminatethe necessity of providing mica insulation between the commutator barsand resultant periormance of the motor or generator on which thecommutator is used due to growing high nuca.

Another objectof my invention is to eliminate the manufacturingdiihculties of a built-up commutator as to correct width of mica betweenbars, symmetry oi the commutator relative to its axis, and holding themica strips parallel to the commutator axis.

Another object of my invention is to prevent the danger of bar edgesbreaking through insulation and leading to grounds through providing anair gap between bars.

Another object of my invention is to reduce the contact resistancebetween the commutator and brushes and thereby improve the operatingcharacteristics of the motor or generator.

Another object of my invention is to reduce arcing 'under the brushesand thereby reducing radio interference.

Another object of my invention is to provide a commutator constructionpermitting the lead wires to be firmly staked to the bars.

Other objects of my invention and the invention itself will become moreapparent from the following description of the drawings wherein:

Fig. 1 is a side elevational view of a commutator shell which I mayemploy;

Fig. 2 is an end elevational View of the shell of Fig. l;

Fig. 3 is a sectional View oi a commutator constructed according to myinvention, taken along a plane including the commutator axis;

Fig. 4 is a transverse section taken along the lines 4 4 of Fig. 3;

Fig. 5 is a side elevational View partially in section oi a commutatorconstructed in accordance with my invention and provided withventilating means;

Fig. 6 is an end elevational view of the commutator of Fig.

Figs. '1 and 8 are views similar to Figs. 5 and 6 respectively .showinga modified construction;

Figs. 9 and 10 are views similar to liigs 5 and 6 respectively showing afurther modified construction;

Figs. 11 and.12v are views similar to Figs. 9 and respectively whereinventilating blades are provided:

Fig. 13 is a side elevational view of a further modi'cation of myinvention;

Fig. 14 is an elevational view of the modiiication of Fig. 13;

Fig. 15 is a section along line L15-i5 of Fig. i3;

Fig.- 16 is an enlarged fragmentary section along line iG-l of Fig. 13,and

Fig. 17 is\a section along line ll-il of Fig. 16.

-Fig. 18 is aside elevational view similar to Fig. 13 but showingVcertain sections broken away for the purpose oiillustration.

Referring now to the drawings, and more particularly to Figs. 1 and 2, Ihave indicated at i@ a generally cylindrical commutator shell includingan axially extending iiange il atone end of the shell and a radiallyoutwardly extending nange il at the opposite `end and a plurality ofradially inwardly extending anchoring lugs i2 intermediate said anges.The shell is formed of molded copper and vgraphite and since the coppermay be molded with any degree of porosity, the graphite may be' moldedtherewith under proper pressure and temperature conditions. The materialof the commutator shell may be either pure copper dust which aftermolding will preferably have a density of approximately 80% or may .bemade of a mixture of graphite in powdered form and copper dust.

The amount of graphite added to the copper is dependent on thelubricating qualities desired as limited by the amount of graphite whichmight be added and still provide a composition forming a good solderjoint. I have found that at least up to 20% by volume of graphite may-be added ltothe copper dust and the resulting molded composition stillprovides a proper solder joint.

Inasmuch as the material of vthe shell is molded rather than spun ordrawn, the shape of the shell may conform closely to the finished shellwith proper allowance for machining, resulting in a minimum of wastematerial. find that although the molded copper, or the molded copper andgraphite composition provides a very hard surface having considerablestrength and which will resist abrasione from the brushes of theelectrical apparatus in which the commutator is located that the moldedmetal is relatively free cutting so that the machining of the commutatorto a desired sizeis not only easier than machining drawn material :butthe material may be machined to closer tolerances. The graphite whenmolded with .the copper is permanently suspended and since the copper isharder than .the material of the brushes, the commutator does not wearto any appreciable extent by contact with the brushes so that a verysmall amount of graphite is freed due to wear of the commutator barsthus eliminating .the .tendency of graphite to fall into the spacebetween 'adjacent bars to cause smudging of the bars and sluggingbetween the bars due to the graphite dust.

The anchoring lugs as best illustrated in Fig. 3, are of dove-tailedform in an axial direction so that the bases of the lugs as indicated ati3 are greater in axial extent than the lugs at the Juncazsaasv turewith the inner walk of the shell. It will be noted by reference to Fig.4 that the lugs i2 extend in a radial direction and that the thicknessof the lugs is substantially constant so that the opening betweenadjacent lugs as indicated at i4 is also substantially of dove tail formin a radial plane.

The shell i@ has a body of insulating material indicated at l5, whichmay be a phenolic con-v.

densate or similar material molded therewith, and which, in a well knownmanner, when subiected to heat, may be poured into a mold andsubsequently hardened. A tube iS, formed preferably of steel or brass,may be molded to the body i to provide a bearing for the commutatoralthough I contemplate that under certain conditions this will not benecessary and the material of body l5 may directly contact the shaftprojected therethrough.

it will be noted that due to 'the dove-tail construction of anchoringlugs i2, together with the dove-tail form of the openings it, a,three-way anchor is provided preventing relative movement between ltheshell l@ and the body i5 in an axial, radial and circumferentialdirection. Also, the axial ends of the anchors i2 are completely em-.bedded in the insulating material so that there is no danger of a shortcircuit through .the anchoring lugs. After molding the body vi5 with theshell it, the shell is separated into commutator bars by radial cuts asindicated at l'l which extend slightly into the insulating material asducting wires may .be soldered in a well known manner. Y

Referring now -to Figs. 5 and 6 I have shown a commutator constructed ina manner similar to that illustrated in Figs. 3 and 4, but wherein a"plurality of ventilation holes i9 are formed in .the

body i5 permitting air to traverse the body and cool the commutator andresultantly the brushes which reduces the tendency of the brushes todeteriorate due to heat and prolongs .the useful life of the brushes.

Figs. 7 and 8 illustrate a modified form of commutator generally similarto that illustrated in Figs. 5 and 6, but wherein a plurality of axiallyspaced metal screenelements 2U are provided through which air must passin traversing the Ventilating holes in body i5. The screen elements 20serve the dual function of reinforcing the body I5 and conducting theheat generated in the commutator to the air holes or Ventilatingpassages.

Referring now to Figs. 9 and 10, I have shown a further modified form ofcommutator similar to that illustrated in Figs. 3 and 4, but wherein aplurality of preferably cylindrical passages 2i are skewed orrunobliquely through .the-insulating body I5 and act as a fan for effectingmovement of air in cooling the commutators.

Referring now to Figs. 11 and 12, I have shown a further modified formof commutator wherein vent holes 22 are provided permitting the passageof air axially to the body i5 and plates 23 embedded in the insulatingmaterial have an end portion as indicated at 24 extending axially beyondthe insulating body to direct air through aaeaasv e may be slewed orextend obliguely through the body l in the manner of the vent holes ofFigs. 9 and lil.

Referring now to Figs. 13 to 18 inclusive, l have shown generally at 25a molded shell which may be formed either of copper or copper andgraphite, the shell including a cylindrical portion 26 having a radiallyoutwardly extending ange 21 and a plurality of anchoring lugs 28 on theinner side of the shell. Intermediate the lugs 28 the flange 21 isprovided with slots 29 extending radially inwardly partially through thecylindrical portion to a point, such as 30, indicated in Fig. 16. In thesame radial zone of each of the slots 29 the inner walls of thecylindrical portion 26 are provided with axially extending preferablyV-shaped grooves 3l extending radially outwardly beyond point 30. Itwill be noted that the slot 2S extends axially along the cylindricalportion beyond flange 21, as indicated at 32, whereby shaving thecylindrical portion by a turning operation to a depth, such as 30, willsever the shell into a plurality of individual bars. This eliminates anexpensive saw cutting or the like operation for severing the bars,although I contemplate that the shell may be divided into bars by sawcuts and in which case the slots 29 act as guides for the saw, moldedwith slots therein similar to slots 29 for guiding the saw or the likesince it is difficult to align the cuts with the embedded lugs l2.

The shell of the modification of Figs, 13 to 18 will have a body ofphenolic condensate material or the like molded therein in the mannerpreviously described which may conform to the modifications of Figs. 1to l2 but the condensate material is preferably permitted to ow into theslots 29 of ange 21 to provide further insulation between the bars.

The material to be shaved from the shell is indicated at 33, Figs. 16and 17. Thus, a molded shell is provided wherein, after molding of theplastic material therein, the shell may be separated into individuallyinsulated bars through removing a thin cylinder of material from thecylindrical portion 26 of the shell by turning in a lathe or the like.

Although I have shown and described preferred form of my invention, Icontemplate that numerous and' extensive departures may be madetherefrom without departing from the spirit of my invention or the scopeof the appended claims.

Having thus described my invention, what I claim is:

l. An article of manufacture, a commutator comprising a body ofinsulating material having an axial shaft receiving perforationtherethrough,

a plurality of commutator bars containing at least 80% copper encirclingsaid body in circumferentially spaced relation, each of said bars havingan anchoring lug extending radially inwardly into said body andprogressively increasing in cross-sectional area radially inwardly, thebody being provided with a plurality of generally axially extending airpassages therethrough, and blades in said passages supported by the bodyhaving their axial end-portions extending beyond the body to direct airthrough said passages.

2. The method of making commutators which includes molding a generallycylindrical shell comprising copper as a chief constituent, the shellbeing formed with radially inwardly extending anchoring lugs on theinner wall of the shell and intermediate the shell axial ends, the shellhaving radially outwardly extending segments having recessestherebetween extending into the shell cylindrical portion, the shellinner wall having axially extending grooves in the radial zone of saidrecesses extending radially outwardly beyond the depth of said recesses,molding a body of 'insulating material within the shell to embed theanchoring lugs, and shaving the external surface of the shellcylindrical portion at least to the depth of said grooves to provideindividual insulated bars anchored in said body.

3. As an article of manufacture, a commutator comprising relativelyspaced commutator segments each comprising a molded mixture, at least80% of said mixture being of finely pulverized copper powder, and thebalance comprising a major portion of finely divided material havinglubricating qualities of substantial electrical conductingcharacteristics.

4. As an article of manufacture, a commutator comprising relativelyspaced commutator segments, at least some of said segments comprising amixture 'of iinely pulverized good electrical oonducting coppermaterial, and finely pulverized graphite, the metallic materialcomprising at least 80% of the volume of the mixture.

5. As an article of manufacture, a commutator comprising a plurality ofrelatively spaced commutator segments, at least one of said segmentscontaining a mixture of finely pulverized copper and graphitic materialhaving respectively good electrical conducting and low frictionalcharacteristics, said material being molded to the solid form of thesegment.

6. An article of manufacture, a commutator comprising a generallycylindrical shell of at least 80% molded copper by volume and 20%graphite by volume, a generally cylindrical body of phenolic condensateof the like insulating material being disposed within the shell, aplurality of generally axially extending air passages disposed throughsaid body, the shell being severed axially thereby providing a pluralityof individual commutator bars anchored to said body.

7. An article of manufacture, a commutator comprising a body ofinsulating material having anA axial shaft receiving perforationtherethrough, a plurality of commutator bars encircling said body incircumferentially spaced relation, each of said bars having an anchoringlug extending radially inwardly into said body, the body being providedwith a plurality of generally axially extending air passagestherethrough, a plurality of o axially spaced screen elements disposedin association with said air passages providing reinforcement for thebody and conducting heat generated in the commutator through said airpassages.

8. An article of manufacture, a commutator comprising a body ofinsulating material having an axial shaft receiving perforationtherethrough, a plurality of commutator bars encircling said body incircumferentially spaced relation, each of said bars having an anchoringlug extending radially inwardly into said body, the body being providedwith a plurality of generally axially extending air passagestherethrough, said air passages being skewed -through the body foreffecting movement of air therethrough.

9. An article of manufacture, a commutator comprising a generallycylindrical body of lnsulating material, a generally cylindrical outershell encircling said body in circumferentially spaced relation, saidshell composed of a mixture of molded copper and graphite powder, aplurality of radially inwardly extending lugs on the shell inner wallsembedded within the body of insulating material, said shell having beendivided intermediate the spaced lugs -to provide anchored individualinsulating commutator bars.

10. An article of manufacture, a commutator comprising a body ofinsulating material having an axial shaft receiving perforationtherethrough. a plurality of commutator bars, containing at least 80%copper and a balance of graphitic material, encircling said body incircumferentially spaced relation, each of said bars having an anchoringiug extending radially inwardly into said body and progressivelyincreasing in cross-sectional area radially inwardly, the body beingprovided with a plurality of generally axially extending air passagestherethrough. and blades in said passages supported by the body havingtheir axial end portions extending beyond the body to direct air throughsaid passages.

. ALVIN CARL BORCHERS,

